Compared to a traditional watch, a smart watch brings additional features such as incoming call notifications, activity tracking, pushing mails or short message service (SMS) messages in addition of displaying time. It can interact with a distant application and display useful information to the user through a panel such as displaying a weather forecast, a caller name photo, instructions of a navigation application, or a map. It can also run local applications related to time (e.g. clock, stopwatch, alarm), health (e.g. activity tracker, step counter, heart rate monitor) that leverage local sensors (e.g. accelerometer, gyroscope, heart rate sensor) and actuators (e.g. vibrator, display).
The need of offering intuitive and convenient user inputs is a key element for these new devices to facilitate human machine interaction. For example, such devices can be controlled by buttons, voice commands, a touch panel, a digital crown (e.g. APPLE WATCH), a rotating bezel (e.g. SAMSUNG GEAR S2), or any combination of these means.
A smart watch may have a small display area and have restrictions in input indicating to perform a function. Therefore, technology of detecting input indicating to perform a function of a smart watch is required.